There are conventional clamps for a disk rotation driver shown in FIGS. 9 and 10 and Japanese Unexamined Patent Application Publication No. 2004-295962.
FIGS. 9 and 10 are sectional views partly showing disk rotation drivers in which FIG. 9 shows a disk dive supporting a single magnetic disk 101 and FIG. 10 shows a disk rotation driver supporting two magnetic disks 101.
In each of FIGS. 9 and 10, the clamp 103 has a central portion fastened to a hub 107 with a screw 105, and a contact portion 109 formed along a periphery of the clamp 103. The contact portion 109 is in contact with a spacer 111 or the magnetic disk 101.
The clamp 103 applies a pressing force to the magnetic disk 101 in a rotation axis direction, thereby fixedly supporting the magnetic disk 101 on the hub 107.
The conventional clamp 103 however has a problem that the pressing force acting on the magnetic disk 101 is unstable.
Namely, when the clamp 103 is fixed to the hub 107 with the screw 105, the central portion of the clamp 103 shifts from a before-fastened state indicated with continuous lines in FIG. 11 to an after-fastened state indicated with dot-and-dash lines in FIG. 11. Due to the shift of the central portion of the clamp 103, the contact portion 109 of the clamp 103 is dislocated and is radially outwardly widened.
As a result, the pressing force of the clamp 103 acting on the magnetic disk 101 spreads to ineffectively press the magnetic disk 101.
Namely, the pressing force of the clamp 103 that presses the magnetic disk 101 weakens, and if an external force such as a shock is applied, the magnetic disk 101 will move to cause a data write or read error.
A frictional force that resists the force of widening the contact portion 109 is variable depending on the state of an interface between the clamp 103 and the magnetic disk 101. This makes the pressing force of the clamp 103 acting on the magnetic disk 101 unstable to deteriorate the disk supporting performance of the clamp 103.